Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “Masseter Muscle”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 1,189 records · Page 66Linked to original sources
PubMed2000

Comparison of cisatracurium-induced neuromuscular block at the masseter and adductor pollicis muscle.

Adequate relaxation of the masseter muscle is important during endotracheal intubation and for the patency of a patient's airway during recovery from anaesthesia. We evaluated onset and recovery from cisatracurium-induced neuromuscular block at the masseter and adductor pollicis muscles. Thirty patients were randomly allocated to receive either 0.1 or 0.15 mg kg(-1) cisatracurium. The evoked response was measured at both muscles using acceleromyography. Onset time was significantly shorter at the masseter muscle than at the adductor pollicis (0.1 mg kg(-1) cisatracurium: 155+/-52 vs. 229+/-44 s; 0.15 mg kg(-1) cisatracurium: 105+/-24 vs. 174+/-35 s). Following 0.1 mg kg(-1) cisatracurium, recovery to a TOF-ratio of 0.7 was faster at the masseter compared to the adductor pollicis (P < 0.05). In the 0.15 mg kg(-1) cisatracurium group recovery of T1 to 75% of control and to a TOF-ratio of 0.7 occurred sooner at the masseter (P < 0.05). We conclude that onset and recovery from cisatracurium neuromuscular block occurs more rapidly at the masseter than at the adductor pollicis. It appears unlikely that residual paralysis is present at the masseter once neuromuscular function at the adductor pollicis has completely recovered.

Adult↗
PubMed1986

Masticatory muscle activity and hyoid bone behavior during cyclic jaw movements in man. A synchronized electromyographic and videofluorographic study.

Synchronized electromyography (EMG) and videofluorography were used to relate the EMG activity from the suprahyoid and masseter muscles and the movement of the hyoid bone to different phases of the jaw open-close-clench cycle. The subjects investigated comprised 19 adult males with normal dentofacial appearances. Five subjects were excluded from the analyses because of a uniform suprahyoid EMG pattern during cyclic jaw movements. The results from the remaining fourteen subjects revealed that mandibular opening was preceded by suprahyoid EMG activity and movement of the hyoid bone in an upward-forward direction. During jaw opening and the first half of the jaw-open phase, EMG activity was registered exclusively from the suprahyoid muscles. The hyoid bone was moved downward-backward during jaw opening. Mandibular closing was preceded by masseter EMG activity and movement of the hyoid bone in a further downward-backward direction. During jaw closing the hyoid bone moved upward and forward. Discrete EMG bursts from the suprahyoid muscles were occasionally registered simultaneously with the masseter EMG activity during jaw closing. No absolute reciprocity existed between suprahyoid and masseter muscle activity during cyclic jaw movements. A period of no EMG activity from either the suprahyoid muscle group or the masseter muscle was noted during the jaw-open phase and the occlusal phase.

Adult↗
PubMed1975

Increases in reflex excitability of monkey masseter motoneurons before a jaw-bite reaction-time response.

Reflex excitability of the motoneurons innervating the masseter muscle of monkeys was tested before a phasic voluntary activation of the jaw-closing muscles (a RT bite response). Single test shocks were delivered to the Mes V which supplies a monosynaptic excitatory input to the jaw-muscle motoneurons. Changes in reflex excitability were assessed by measuring the amplitude of the synchronous muscle potential evoked by the test shock. Amplitudes of the muscle potentials evoked by shocks which occurred just before the beginning of the voluntary EMG response, as judged by the onset of EMG activity of the masseter muscle contralateral to the test shock were many times larger than potentials evoked immediately following the visual RT stimulus. Curves relating the average amplitude of the evoked response to its time before the beginning of the voluntary response suggest that the reflex excitability of the motoneuron pool begins to increase 25-45 ms before the first detectable EMG activity occurs. These results suggest that inputs arrive at the motoneurons of agonist muscles used in rapid RT tasks substantially before changes in the EMG of the muscle are noted. These results, in part, would account for the time interval noted between the beginning of neural activity in suprasegmental structures which presumably excites spinal motoneurons, and the first EMG activity of muscles which are innervated by these motoneurons.

Animals↗
PubMed1976

[Sarcosporidiosis in sheep (author's transl)].

Histological examination of the masseter muscle, diaphragm, oseophagus and heart showed that about 18 per cent of approximately eight-month-old sheep in the Netherlands were infected with Sarcocystis. The masseter muscle obviously was the site of predilection.

Animals↗
PubMed2005

Peripheral NMDA receptor modulation of jaw muscle electromyographic activity induced by capsaicin injection into the temporomandibular joint of rats.

We have previously documented that peripheral N-methyl-d-aspartate (NMDA) receptor mechanisms are involved in nociceptive reflex increases in jaw muscle activity to injection of mustard oil or glutamate into the rat temporomandibular joint (TMJ). The aim of the present study was to determine whether peripheral NMDA receptor mechanisms are also involved in the nociceptive reflex responses in the jaw muscles evoked by injection of the inflammatory irritant and algesic chemical capsaicin into the TMJ. The effects of peripheral injection of NMDA receptor antagonists, MK-801 and APV, on the increases in electromyographic (EMG) activities of digastric and masseter muscles reflexly evoked by capsaicin injection into the TMJ were tested in halothane-anesthetized male rats. The capsaicin injection following pre-injection of vehicle evoked significant increases in EMG activity in both digastric and masseter muscles whereas pre-injection of MK-801 or APV into the TMJ resulted in a significant concentration-related reduction in the magnitude of capsaicin-evoked digastric and masseter EMG activity (ANOVA-on-ranks, P < 0.05). This finding indicates that capsaicin-evoked digastric and masseter EMG activity can be attenuated by pre-injection into the TMJ of NMDA receptor antagonists, and that the activation of peripheral NMDA receptors may be important in the mechanisms whereby capsaicin evokes nociceptive trigeminal responses.

Analysis of Variance↗
PubMed1998

[The correlations between the echographic aspect of the perioral and masticatory muscles and dento-skeletal characteristics].

INTRODUCTION: US of some muscular components of the stomatognathic system (orbicularis oris and masseter muscles) has proved to provide important information about their morphologic features. The purpose of this study is to explore the US features of the perioral and masticatory muscles in patients affected with any type of malocclusion and to analyze the correlations between dento-skeletal characteristics and muscle changes. MATERIAL AND METHODS: We examined 26 untreated patients (10 men and 16 women); we measured their cephalometric parameters on lateral skull teleradiographs and then we measured with US both the masseter and orbicular muscles dimensions. The US images were acquired with 5 MHz and 7.5 MHz probes, measuring the masseter muscle with transversal and longitudinal scans, and the two parts of the orbicularis oris with longitudinal scans. The cephalometric measures were calculated with: angular parameters useful to determine the sagittal relationships, both angular and linear parameters to define the vertical relationships and angular measures that define the incisor position. We applied the Spearman test to assess if there was a relationship between the US dimensions of the orbicularis oris and the masseter, and the dento-skeletal characteristics of these 26 patients. RESULTS: Our results show that there is a strong correlation between mandibular morphology, the palatal plane, respectively, and the masseter length. There is a direct correlation with the masseter dimension for the palatal plane obliquity, and an inverse correlation for the mandibular morphology. The incisor position is influenced by the orbicular oris muscle dimension and by the asymmetric position of the superior and inferior incisors. CONCLUSIONS: This noninvasive diagnostic examination is a useful aid to the clinical examination of the muscles, especially in orthodontic diagnosis, together with MRI and CT, respectively more expensive and unhealthier.

Adolescent↗
PubMed1988

Histochemical fiber type composition in 12 skeletal muscles of miniature pigs.

In 12 skeletal muscles of adult miniature pigs histochemical fiber type analysis was performed. Longissimus dorsi, psoas major, diaphragm and fore- and hind-limb muscles were composed from SO, FOG and FG fiber types showing characteristic clump distribution. The muscles differed in the first place by the frequencies of SO and FG types (7-70% and 19-79% respectively); the proportion of FOG type varied considerably less (10-32%). On the other hand in the masseter muscle only SO and FOG types with a mosaic distribution were demonstrated (28% and 72% respectively). In the majority of muscles the prevailing fiber type has also the largest diameter, but the differences between individual types were mostly insignificant. The largest diameter was found in the masseter muscle fibers--around 70 microns, which is 20-30 microns more than in the other muscles.

Animals↗
PubMed1988

New enrichment method for isolation of pathogenic Yersinia enterocolitica serogroup O:3 from pork.

A new enrichment medium for the recovery of pathogenic Yersinia enterocolitica serogroup O:3 from naturally infected meat products based on three selective agents, Irgasan, ticarcillin, and potassium chlorate (ITC), was compared with several other one- or two-step enrichments. Y. enterocolitica serogroup O:3 was recovered from 96.5% of 29 pork tongues, 24% of 50 ground pork samples, 16% of 25 masseter muscle samples, and 61% of tonsils. ITC was by far the most sensitive method for the recovery of Y. enterocolitica O:3, especially from ground meat and masseter muscles, while cold and two-step enrichments yielded better results for nonpathogenic strains. Plating of ITC enrichments onto SS-deoxycholate-calcium agar gave overall better results than plating onto cefsulodin-Irgasan-novobiocin agar for serogroup O:3.

Animals↗
PubMedDate not supplied

Reproducibility of the electromyogram.

Electromyographic recordings of masseter muscles were taken during mastication without the introduction of an experimental variable. The amplitude, duration, and sequence of the onset of muscle bursts were used to evaluated the recordings. Amplitude showed the most variation during the same session, at different sessions, and between three different areas of the masseter muscle. Onset showed the least variation during the same session and at different sessions; duration showed the least variation between areas.

Adult↗
PubMed2004

Significance of coil orientation for motor evoked potentials from nasalis muscle elicited by transcranial magnetic stimulation.

OBJECTIVE: In transcranial magnetic stimulation (TMS) of the motor cortex, the optimal orientation of the coil on the scalp is dependent on the muscle under investigation, but not yet known for facial muscles. METHODS: Using a figure-of-eight coil, we compared TMS induced motor evoked potentials (MEPs) from eight different coil orientations when recording from ipsi- and contralateral nasalis muscle. RESULTS: The MEPs from nasalis muscle revealed three components: The major ipsi- and contra-lateral middle latency responses of approximately 10 ms onset latency proved entirely dependent on voluntary pre-innervation. They were most easily obtained from a coil orientation with posterior inducing current direction, and in this respect resembled the intrinsic hand rather than the masseter muscles. Early short duration responses of around 6 ms onset latency were best elicited with an antero-lateral current direction and not pre-innervation dependent, and therefore most probably due to stimulation of the nerve roots. Late responses (>18 ms) could inconsistently be elicited with posterior coil orientations in pre-innervated condition. CONCLUSIONS: By using the appropriate coil orientation and both conditions relaxed and pre-innervated, cortically evoked MEP responses from nasalis muscle can reliably be separated from peripheral and reflex components and also from cross talk of masseter muscle activation.

Adult↗
PubMed1978

Masticatory function after activator treatment. An analysis of masticatory efficiency, occlusal contact conditions and EMG activity.

Masticatory function was investigated in nine patients with relapse and ten patients without relapse of overjet after activator treatment, Masticatory efficiency, evaluated by a chewing test, was related to the number of intermaxillary tooth contacts and the electromyographic (EMG) activity from the temporal and masseter muscles during chewing. The results of the investigation indicated that a reduced masticatory efficiency was connected with fewer intermaxillary tooth contacts and less EMG activity from the temporal and masseter muscles. In patients with relapse of overjet, masticatory efficiency and muscle activity was reduced in comparison with patients without relapse. The relationship between the number of tooth contacts and masticatory efficiency was poor in the relapse patients. Unstable occlusal conditions and atypical tongue function may be an explanation.

Activator Appliances↗
PubMedDate not supplied

The origin of R2 of the blink reflex recorded on the affected side of patients with complete facial nerve paralysis.

The possible mechanisms contributing to the generation of R2-like response were investigated in 19 patients with complete facial nerve paralysis, where the efferent limb of the reflex arc is absent. The first possibility that potentials produced by the unaffected orbicularis oculi (0.0c) are conducted to the reference electrode taped over the nose was confirmed as the amplitude of R2 on the affected side was significantly reduced when the reference electrode was removed from the nose and taped on the ear lobule. The second possibility of volume conducted potentials produced by muscular generator in temporalis and masseter muscles through trigemino-trigeminal reflex was suggested in some patients based on three reproducible observations: (1) EMG activity of high amplitude could be recorded with electrodes taped over the affected 0.0c muscle during voluntary teeth clenching, (2) R2-like responses were recorded in patients with bilateral complete facial paralysis, (3) R2-like responses were recorded from temporalis and masseter muscles. The contribution of extraocular muscles could be discounted as R2 could be recorded from patients with Möbius's syndrome who had complete bilateral facio-ocular paralysis. The results of the present study further support the greater value of R1--rather than R2--in predicting clinical outcome of patients with peripheral facial nerve palsy.

Action Potentials↗
PubMed2006

Muscle inflammation induces a rapid increase in calcitonin gene-related peptide (CGRP) mRNA that temporally relates to CGRP immunoreactivity and nociceptive behavior.

Recent data support an important role for calcitonin gene-related peptide (CGRP) in deep tissue nociceptive processing. Using real-time reverse transcriptase polymerase chain reaction (RT-PCR), radioimmunoassay, immunohistochemistry and behavioral testing, we studied the early time course of CGRP mRNA and protein expression as well as nociceptive behavior following muscle inflammation. A rapid and significant increase in CGRP mRNA occurred in the mandibular division (V3) of the ipsilateral trigeminal ganglion at 30 minutes, 4 and 24 h after the injection of complete Freund's adjuvant as an inflammatory agent into rat masseter muscle. No change in mRNA occurred in the ipsilateral ophthalmic and maxillary divisions (V1/V2) or in the contralateral V3. The levels of immunoreactive calcitonin gene-related peptide (iCGRP) in the ipsilateral V3 significantly increased at 1, 4 and 24 h following muscle inflammation. In contrast, no change occurred in iCGRP levels in either the ipsilateral V1/V2 or contralateral V3. When saline was injected into the masseter muscle, the levels of mRNA or iCGRP did not change in the ipsilateral V3 suggesting that the biochemical changes are specific to CFA-induced muscle inflammation. The number of muscle afferent neurons immunoreactive for CGRP was significantly reduced compared with control at 1, 4 and 24 h in the ipsilateral but not in the contralateral trigeminal ganglion following inflammation. This decrease in the ipsilateral ganglion may indicate a loss of intrasomatic CGRP as a result of increased axonal transport away from the neuronal cell body and/or release of CGRP. Behavioral testing showed a reduction in head withdrawal thresholds bilaterally from 30 min through 24 h following muscle inflammation. Thus upregulation of CGRP mRNA and iCGRP levels are temporally related to the development of inflammation and lowered pain thresholds. The present data support the hypothesis that CGRP is upregulated during deep tissue inflammation and suggest that gene transcription is involved in this upregulation.

Animals↗
PubMed1987

Mandibular movements and jaw muscles' activity while voluntarily chewing at different rates.

As a way of learning about the motor control of chewing, we studied how well a subject could voluntarily chew in time with a metronome and defined the changes in the spatial and temporal aspects of the chewing pattern with changes in chewing rate. Timing and extent of mandibular movements were assessed in nine adults from Kinesiograph recordings; timing and level of activity in digastric and both masseter muscles were determined from surface EMGs. Each subject chewed gum in time with a metronome set randomly at 46, 100, 160 beats per minute or at a frequency close to his automatic chewing rate. Cycle-by-cycle analysis showed that subjects varied in their ability to keep pace with the metronome. When chewing at high frequencies, six subjects reduced gape, three did not. Contralateral deflection in opening, when present, was significantly reduced when chewing at high frequencies and this decrease was independent of vertical gape. Durations of opening, closing, and occlusal phases decreased in proportion to the decrease in total cycle duration. Burst duration of diagastric activity decreased about 29% compared with a 77% decrease in cycle duration over all chewing rates. At low frequencies onset of digastric activity occurred after onset of opening. At high frequencies digastric onset preceded opening. Burst durations of both masseter muscles decreased in concert with the decrease in cycle duration. Termination of activity in both masseters was synchronous and always occurred 100 +/- 20 ms prior to the next opening. Therefore, we conclude that (i) individuals vary in ability and strategy for controlling chewing rate voluntarily and (ii) with increases in chewing rates the shortening of burst duration for the digastrics is significantly less than for the masseters.

Adult↗
PubMed1987

Alpha-adrenergic receptor subtypes in the cerebral circulation of newborn piglets.

The purpose of this study was to identify the alpha-adrenergic receptor subtype mediating cerebral vasoconstriction during sympathetic nerve stimulation in the newborn piglet. The effect of alpha 1- and alpha 2- antagonists prazosin and yohimbine on the cerebrovascular response to unilateral electrical stimulation (15 Hz, 15 V) of the superior cervical sympathetic trunk was studied in 25 newborn piglets. Regional cerebral blood flow was measured with tracer microspheres (15 +/- 1 micron). Sympathetic stimulation decreased blood flow to the ipsilateral cerebrum hippocampus, choroid plexus, and masseter muscle by 15 +/- 2, 10 +/- 2, 51 +/- 5, and 94 +/- 5%, respectively. alpha 1-Adrenergic receptor blockade with prazosin (0.5 mg/kg, n = 10) inhibited the sympathetic vasoconstriction in the cerebrum, hippocampus, and masseter muscle (7 +/- 2, 4 +/- 3, and 55 +/- 9%, respectively) and abolished it in the choroid plexus. alpha 2-Adrenergic receptor blockade with yohimbine (0.5 mg/kg, n = 6 and 1.0 mg/kg, n = 5) had no effect. Following the higher dose of yohimbine, however, blood flow to all brain regions was increased by approximately two-fold, possibly due to enhanced cerebral metabolism. These data demonstrate that vascular alpha 1-adrenergic receptors mediate vasoconstriction to neuroadrenergic stimulation in cerebral resistance vessels in the newborn piglet.

Animals↗
PubMed2005

Preliminary rapport on head posture and muscle activity in subjects with class I and II.

Forward head posture may cause alterations in the stomatognathic system, including changes in the muscle activity of the masticatory muscles and dental occlusion alterations. Considering the need for further understanding of the relationship between the stomatognathic system and the cervical region, the purpose of this study was to analyse the head posture and the electromyographic (EMG) activity of the anterior portion of temporal and masseter muscles bilaterally among bruxist's subjects with different dental occlusion classifications using the Angle method. The study consisted of 20 female volunteers, between the ages of 17 and 27 years. They were separated into two groups (class I and class II occlusions) according to a dentist-performed evaluation. An assessment of forward head posture was conducted using a photographic technique (angular calculus) combined with a clinical analysis. In the EMG analyses, active differential surface electrodes (Ag) were utilized and were placed bilaterally on the belly of masseter and temporal muscles, perpendicular to the muscles fibres. The EMG signal recorded during bilateral isotonic mastication, was presented using the Root Mean Square and was processed by Matlab software. The results indicated that the EMG responses of temporal and masseter muscles tend to be modified by occlusion alteration class II. Subjects with class II occlusion tended to present more occurrence of forward head posture with alterations in the muscle activity pattern between masseter and temporal muscles.

Adolescent↗